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Optical Information Datasheet

So you would like a large lens with a high magnification?

We are asked this every day!  Usually because the customer has searched and searched and cannot find what they think they want – there is a very good reason for this.

With a single lens system the relationship between magnification and lens size is subject to the Immutable laws of Physics. (see later about a multiple lens system)

With a single lens magnifier a higher magnification ALWAYS means a smaller lens, shorter working distance, shorter eye point and a thinner depth of field.

The only way to deliver higher magnifications with a larger output display is to purchase a digital magnifier. (see later)

Do not confuse Diopters with Magnification, they are related but different (see table and explanation below).  Many vendors provide incorrect information mixing these two values – be aware.

Here are some approximate magnifications and the resultant lens sizes for single lens magnifiers. If anyone says they can do better they are misleading you.  They may have a big area of glass but if it is unusually large only the central area will have a usable image.

Table of Magnifications of Single Lens Magnifiers
(data is from the very best quality lens manufacturers, most other manufacturers have much smaller values)

Magnification

Diopters

Approximate Typical
Maximum Diameter
​​​​​​​of the Area of a Lens that delivers a usable image (mm)

Working Distance (mm)

Distance from bottom of lens to point on the subject that is in focus

Eye Point (mm)

Distance from top of lens to your eye when subject is in focus through the lens
 (in reality there is usually a range of distances with variable magnification factors)

1.75X

3

180

170

160

2.25X

5

170

150

150

3X

8

130

130

150

6X

20

105 (usually much smaller)

82

100

10X

36

85 (usually much smaller)

43

80

15X

56

70 (usually much smaller)

30

65

Diopters

Diopter refers to the curvature of the lens. As the diopter increases, the lens become thicker and the curvature greater. As the curvature increases, light rays are redirected to fill a greater portion of the viewer’s retina which makes the object look bigger.

There is more than one formula to converts the diopter of a lens into its power, the commonly used formula is: Magnification = (Diopter / 4) +1.

Digital Magnifiers

Digital magnifiers break the link because the ‘output’ part is no longer a property of the lens.  It becomes a display and the screen can be any size – in other words the camera in the Digital Magnifier magnifies the image from the lens to the display.  It is the ONLY way to get a higher magnification with a single lens system with a larger display of the image.

What is a two or multiple lens system?

In its most simplistic sense it is one lens looking at the central part of another lens, both magnify.  The sum of the two magnifications produces a much higher magnification.  A classic example of a two lens magnifying system is a microscope which has eyepieces (lenses) which look at an objective lens below.  But the output image to the eyepiece (as with binoculars) is tiny so you have to place your eye close to the output lens/eyepiece.

What is a magnifier?

A magnifier (i.e. magnifying lens) is a lens or combination of lenses used to magnify (or enlarge) an object. Magnifiers and magnifying glasses enable people to magnify a variety of objects (e.g. books, newspapers, fine print, stamps, coins, antiques, art, jewelry, gemstones, foliage, insects, and rocks). 

Who invented the magnifier?

The magnifying glass was invented in 1250 by Roger Bacon.

What types of magnifiers are there?

When it comes to magnifiers, most people probably think of the classic hand-held magnifying glass used by Sherlock Holmes. However magnifiers come in a wide variety of shapes, sizes and magnifications. At Cambridge Optics, we stock over 250 different magnifiers! In addition to Hand-Held Magnifiers, we also carry Hands-Free Magnifiers, Illuminated Magnifiers, Page, Bar & Dome Magnifiers, Loupes, Linen Testers, Digital Magnifiers & Stand Magnifiers, Pocket Magnifiers, Reading, Specialty Glasses, Microscopes, Portable Microscopes & Binoculars.

What are magnifying lenses made of?

Magnifier and magnifying glass optical lenses can be made of glass or acrylic (plastic) materials. Each type of lens has advantages and disadvantages when compared to the other.
Generally, glass lenses allow more light to be transmitted through the lens and usually have very clear optical qualities. It is hard, but not impossible, to scratch a glass lens. A glass lens is generally heavier than an acrylic lens of the same size.

Acrylic lenses are used as an alternative to glass lenses. They are usually very lightweight compared to glass lenses. Acrylic is the common name for Poly(methyl methacrylate) (PMMA), a thermoplastic or transparent plastic, created in 1928. Its composition normally prevents breakage and shattering and it is normally scratch-resistant. With modern technology, it has become possible to produce magnifiers with exceptional optical qualities using an acrylic lens. A majority of today’s magnifier lenses come with a high quality acrylic lens